This invention relates to receptor paper stripping apparatus for use in electrophotographic machines.
As is well known in the art, in an electrophotographic machine it is essential to effectively strip away a printing sheet or a receptor paper from a photosensitive drum after transfer printing a toner or powder image formed thereon onto the receptor paper in order to obtain a satisfactory copy and to prevent failure of the machine. Since an electrostatic latent image is formed on a photosensitive element carried by a rotary drum, and the latent image is developed by applying a powder of toner onto the latent image by the electrostatic attractive force, after completion of the transfer printing there is a tendency that the receptor paper will be adhered to the rotary photosensitive drum by the electrostatic attractive force caused by the latent image. This tendency will be enhanced when the transfer printing is performed under the action of a corona discharge unit as will be described later. When a stripping roller is used to remove the receptor paper from the photosensitive drum, as the receptor paper is rapidly separated away from the stripping roller the potential difference between the surface of stripping roller and the receptor paper increases suddenly thus causing electric discharge by the Paschen' s Law. As a result, the powder of the toner that has been transferred onto the surface of the receptor paper and held thereon by the electrostatic attractive force will be scattered with the result that characteristic scale shaped or tree root shaped discharge patterns are formed on the receptor paper thereby greatly degrading the quality of the reproduced copy.
Heretofore, various receptor paper stripping apparatus have been proposed including a type wherein compressed air is blasted to the interface between the receptor paper and the photosensitive drum, a type wherein a vacuum suction is applied on the back of the receptor paper, a type wherein mechanical pawls are used to separate the receptor paper from the photosensitive drum and a type wherein endless rotating belts are used. However, they cannot accomplish the desired object of effectively stripping off the receptor paper with simple and inexpensive construction.